The present invention relates to a device for electrostatically charging a multilayer ribbon or paper web train.
It is generally known and described in EP 0 230 305 A2 that in rotogravure printing the incoming material webs, or respectively paper web trains or ribbons, are made to adhere to each other electrostatically, which adherence is called ribbon adherence. The stability of the material webs or paper web trains is increased by means of this electrostatic interlocking, so that the danger of a formation of corners of the printed products in the folding apparatus is reduced. Electrodes, which are arranged at both sides of the material webs and at a distance from the material webs are provided for applying the electrostatic charge.
In connection with this electrostatic charge, its low effectiveness on the paper web train or ribbon is disadvantageous, so that it became necessary to arrange additional devices, for example electrostatically charged guide devices, as disclosed in EP 0 230 305 A2 in order to reduce the effects of the so-called whip action, which leads to the formation of corners.
DE 31 17 419 C2 describes a method for the electrostatic charging of a multilayer paper web train ribbon. Here, the ribbon is charged by means of contactless acting electrodes after the webs have been brought together to form a ribbon downstream of a pair of compression rollers.
DE 27 54 179 C2 discloses a method for the electrostatic charging of a multilayer ribbon, wherein the edge areas of each layer are individually charged by means of rollers.
EP 0 378 350 A2 discloses a transport device for paper sheets in a plotter. This transport device has transport rollers for electrostatically charging a paper sheet and a plastic sheet.
U.S. Pat. No. 4,462,528 A describes a device for holding a web. This device has brushes, by means of which the web is held electrostatically.
The object of the present invention is based on providing a device for the electrostatic charging of a multilayer ribbon.
In accordance with the present invention, the object of the present invention is attained by the use of two rollers that are placed in opposition to each other and which are provided with opposing electrical charges. These rollers, which press the rubber or paper web train together, also act as charging electrodes. The multilayer paper ribbon is adhered together by the charge imparted to it from the roller pair. Alternatingly, the paper web train or ribbon can be electrostatically charged by oppositely polarized charge electrodes in the form of electrically conductive brushes which touch the printing paper web train or ribbon.
The advantages which can be achieved by means of the present invention lie, in particular, in that charging of the paper web train or ribbon takes place in a manner which is so lasting, that further devices for preventing, or reducing the formation of corners can be omitted. For example, an already provided pair of drawing rollers, which is required for the operation of the folding apparatus and has been modified in its design for the purpose of transmitting a voltage, is used as the device for charging the ribbon.
The strength of the voltage required for charging the ribbon is reduced in comparison with the voltage required by the prior art.